The invention relates to a control method for a frame transfer sensor in an image pick-up device to obtain black level information in a picture signal, the sensor including an image section comprising sensor image elements arranged in rows and columns for converting incident radiation into charge packet information as picture information, a sensor black level section coupled thereto, and a storage section coupled thereto for the purpose of picture information storage comprising sensor storage elements arranged in rows and columns and a parallel-in, series-out shift register section coupled thereto comprising at least one row of sensor shift register elements, said black level, storage and register sections being shielded from radiation, the device for performing the control method including a time signal generator for applying at least clock pulse signals to control electrodes of the sensor so that after a picture information integration period a frame information transfer via the columns is effected from the image section to the storage section, whereafter row after row and periodically a parallel information shift in the storage section and a parallel information transfer from the storage section to the shift register section is effected, between which parallel information transfers the shift register section each time has a serial information shift to an output of the sensor for supplying the picture signal comprising picture information and black level information associated with the sensor elements.
The invention also relates to an image pick-up device suitable for use of the method.
Such a method and image pick-up device are known from U.S. Pat. No. 4,635,126. This Patent describes the frame transfer after the picture information integration period from the black level section and the image section to the shift register section and the storage section. Subsequently, the black level information followed by the information which has been picked up becomes available at the sensor output. The Patent states that the black level information is subsequently utilized for combining a control of the picture information integration period and of a signal amplification factor.
It appears that the known control method starts from the fact that after the last, picked-up picture information has passed through the black level section an initial black level reference is present in this section. During the next picture information integration period black level information is subsequently accumulated in the black level section as from the initial black level reference. The local black level accumulation must be effected in sensor elements each covering an element area, i.e. reference area which is as large as that at the pick-up elements.
The known control method implicitly starts upon a correctly laid down initial black level reference in the correct reference area. This starting point need not be applicable to all known control methods.